Improve the numpy test/warning

The Pythonic way to see if something has been
imported is to test whether it is in sys.modules.

And add tests to validate that the numpy warning gets
issued or not depending on the state of the environment.
We use the new source_override() function, since these new
tests aim to test the python_worker behavior as it evolves.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ctrueden

src/appose/python_worker.py

@@ -290,7 +290,7 @@ def main() -> None:
         numpy_installed = any(
             dist.metadata["Name"] == "numpy" for dist in distributions()
         )
-        if numpy_installed and "numpy" not in globals():
+        if numpy_installed and "numpy" not in sys.modules:
             print(
                 "[WARNING] This environment includes numpy, but numpy was not imported via a service init script.",
                 file=sys.stderr,

tests/test_python_worker.py

@@ -0,0 +1,49 @@
+# Appose: multi-language interprocess cooperation with shared memory.
+# Copyright (C) 2023 - 2026 Appose developers.
+# SPDX-License-Identifier: BSD-2-Clause
+
+
+from pathlib import Path
+
+
+import appose
+
+from tests.test_base import source_override
+
+
+def _numpy_env():
+    return (
+        appose.uv()
+        .include("numpy")
+        .env(**source_override())
+        .base("target/envs/pyworker-numpy")
+        .log_debug()
+        .build()
+    )
+
+
+def test_numpy_warning():
+    """Tests that a warning is issued when numpy is installed but not imported via init."""
+    env = _numpy_env()
+    with env.python() as service:
+        service.task("pass").wait_for()
+        error_lines = service.error_lines()
+    assert any("[WARNING]" in line and "numpy" in line for line in error_lines)
+
+
+def test_numpy_no_warning():
+    """Tests that no warning is issued when numpy is imported via the init script."""
+    env = _numpy_env()
+    with env.python().init("import numpy") as service:
+        service.task("pass").wait_for()
+        error_lines = service.error_lines()
+    assert not any("[WARNING]" in line and "numpy" in line for line in error_lines)
+
+
+def test_no_warnings():
+    """Tests that no warning is issued in numpy-free environments."""
+    env = appose.system()
+    with env.python() as service:
+        service.start()
+        error_lines = service.error_lines()
+    assert not any("[WARNING]" in line for line in error_lines)